From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABBB9C433F5 for ; Mon, 7 Feb 2022 18:33:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229488AbiBGSc6 (ORCPT ); Mon, 7 Feb 2022 13:32:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233253AbiBGSbe (ORCPT ); Mon, 7 Feb 2022 13:31:34 -0500 Received: from mail-lj1-x22e.google.com (mail-lj1-x22e.google.com [IPv6:2a00:1450:4864:20::22e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A8A06C0401D9 for ; Mon, 7 Feb 2022 10:31:33 -0800 (PST) Received: by mail-lj1-x22e.google.com with SMTP id z7so20975811ljj.4 for ; Mon, 07 Feb 2022 10:31:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=NddTA8JTEM8uEkIveiNRta0hpicmCOBMWm+eYHHc8p8=; b=IWuDFDU4wr0TiaPoaW3kU1CsX3fnzJMnTSop6BprigMbs90GF/cdHHKM7rF4pEE4WI mlnsP6VI6SmNyZwlryimRJDrModfe4+U0uePAo3vb+Fs1P4LVlM01a1vuwmcJzJ+BhX9 wtQPBaN2qUPAsTj2NK+NDnBb3I/LUZ88RqBsmpSKjeyqnjz51RecaN3iv/qBt3t4KPvF 2iU5WBPtOTJK+k/hpKekECzjJeqwgBrjVf+BChiVNpM7iNRl8hGf+CfiNeFxpn+CiP56 i5jvxeRyGK/0RA3BvUIhXR+1zUdYau+UqwYjmWEtlOe/JxNutp5y7uzP6KbCSod2Wj6R s87w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=NddTA8JTEM8uEkIveiNRta0hpicmCOBMWm+eYHHc8p8=; b=dHqXmrhU5rOdaCR7YWV6qEUVE785vp19kVRaIxgWqouhgyI8ZHACr3l79GRb5Xn6jG WBTLPIQPOAptz6bCIz9N/KsglMuuKYXNQoXKKOD+3B5avzlrDejpFRmND/DRoSqHaIPF 9aw6WD4SMzXOLm8/doMPWoUte12XQ1isKRe7gumkI2JFl9f5Un18sk2uTuB+h4TVUEeW EpuicqijXUeYLkNTMdubBAL5EGp5VEAVD+NlApSNTeAHh4zXvMonYAruSsDWVqrdw49n Jl0A/GL5WXGrkU6NDANJYRagbJ2ZPPHbBMTNi+Jgc84UdEaF/fL5O0exTP3IM3vGSuck xHGA== X-Gm-Message-State: AOAM532cVLojjqw8QcqLuPifIooQZ6TE21XrJexHsG0tTCC7FZXWwEi7 czgz0fHGpNtzYgOlPKDG3nQkJw== X-Google-Smtp-Source: ABdhPJzS7ltlwsGJn6FZ15E+lK+3hhf4ZXz0pU4Wl811KANBgWF+2pB0plDEmASKTBGFh0MNaO8llA== X-Received: by 2002:a2e:9847:: with SMTP id e7mr499578ljj.238.1644258692051; Mon, 07 Feb 2022 10:31:32 -0800 (PST) Received: from [192.168.0.102] ([217.71.236.28]) by smtp.gmail.com with ESMTPSA id y17sm81028lfk.57.2022.02.07.10.31.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Feb 2022 10:31:31 -0800 (PST) Subject: Re: [PATCH 2/9] dt-bindings: i2c: qcom-cci: add description of a vbus-supply property To: Mark Brown , Wolfram Sang Cc: Bjorn Andersson , linus.walleij@linaro.org, Loic Poulain , Robert Foss , Rob Herring , linux-i2c@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org References: <20220203164629.1711958-1-vladimir.zapolskiy@linaro.org> <20220203164629.1711958-3-vladimir.zapolskiy@linaro.org> <846cdc17-891d-2ee4-fc89-7cf6fbdebc1d@linaro.org> From: Vladimir Zapolskiy Message-ID: <682b7ffe-e162-bcf7-3c07-36b3a39c25ab@linaro.org> Date: Mon, 7 Feb 2022 20:31:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On 2/7/22 4:39 PM, Mark Brown wrote: > On Mon, Feb 07, 2022 at 04:08:01PM +0200, Vladimir Zapolskiy wrote: >> On 2/4/22 9:32 PM, Mark Brown wrote: > >>> Oh, good. I forsee no problems here. Probably this is something that >>> should be in the I2C core if it's going to be dynamically managed, >>> though just setting the supply as always on is probably more expedient. > >> vbus-supply property has been added recently to another I2C master controller, >> see commit c021087c43c8 ("dt-binding: i2c: mt65xx: add vbus-supply property"). > > Note that some devices do have supplies that I/O is referenced against > and it's not clear that this isn't what's goin on here. > >> It serves right the same purpose, and its handling is going to be done in i2c >> core, however since the latter is not yet completed, I would propose to add >> the property to i2c-bus subnodes of QCOM CCI and its support in the driver, >> later on both the property and its generic support would be better to see in >> i2c core. > > The bindings are ABI, it doesn't seem like a good idea to add new ABI as > a temporary bodge. The bindings are supposed to describe hardware, thus it's natural to extend them, I believe there is a trilemma in this particular case: 1) add optional vbus-supply property to all I2C master controllers or I2C busses in case of multiple I2C busses managed by a single controller, 2) add optional vbus-supply property to all I2C slave devices, 3) ignore peculiarities of particular (multiple in fact) PCB designs and a necessity of adding a regulator finely described as a pull-up for I2C bus lines. My assumption is that a decision should be generic for all similar cases, Wolfram, could you share your point of view on the subject? -- Best wishes, Vladimir